Safety switch and associated methods

ABSTRACT

A cable pull switch includes a polychotomous sensor configured to provide a reading of at least one of a plurality of values, the reading corresponding to a tension on a pull cable or a linear displacement of an end of a pull cable. A processor coupled to the polychotomous cable pull sensor configured to determine a rate of change of the value of the reading from the sensor and determine an occurrence of a cable pull event, the determination based on the determined rate of change of the value, and determine whether the rate of change of the value of an electrical resistance through the polychotomous cable pull sensor is below a threshold rate of change value, and adjust an upper pull threshold value to a new upper pull threshold value that is based on a present reading of the value of the electrical resistance through the strain gauge.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/385,635, filed Apr. 16, 2019, and entitled “Safety Switchand Associated Methods,” which is a divisional application of U.S.patent application Ser. No. 15/815,087, filed Nov. 16, 2017, whichissued as U.S. Pat. No. 10,304,648 and entitled “Safety Switch andAssociated Methods,” which is a divisional application of U.S. patentapplication Ser. No. 14/943,650, filed Nov. 17, 2015, which issued asU.S. Pat. No. 9,824,841, and entitled “Safety Switch and AssociatedMethods,” each is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure generally relates to methods and systems for asafety switch, and more particularly to new methods and apparatuses toimplement a cable pull safety switch feature.

BACKGROUND

Emergency stop devices are devices that help ensure safe workingconditions for personnel working in and around machinery. Such machinerymay exist, for example, in factory settings, manufacturing settings,agricultural settings, foundry settings, warehouse settings, or otherindustrial settings. Often, the machinery (e.g., industrial presses, diemachines, milling machines, molding machines, robotics, conveyor belts,etc.) may include moving parts or other hazards that can be dangerous tothe personnel working around the machinery. In the event of a dangeroussituation where the safety of a worker may need to be maintained, anemergency stop device can be actuated to immediately cease operation ofthe particular machine. By providing one or more emergency stop deviceswithin quick reach of workers, injury can be avoided or mitigated.

One commonly used emergency stop device is a cable pull switch (alsocalled a grab wire switch, a safety rope switch, or other similarnames). A cable pull switch is coupled to one or both ends of arelatively inelastic cable (e.g., a steel cable). When properlyinstalled, pull cable exerts a tension on the cable pull switch. Soconfigured, a long distance (e.g., 100 meter or more) of pull cable canprovide a nearly continuous emergency stop function that is easilyactivated around machinery or along conveyor belts. Any notabledeflection or force exerted on the pull cable (e.g., by a worker pullingon the pull cable) can trigger the cable pull switch to effect anemergency stop of the machinery or equipment to which it is connected.

Existing cable pull switches utilize mechanical contact blocks withbinary on/off or open/closed states. These existing cable pull switchesact like a snap action switch where a transition between an on and offstate occurs almost instantaneously in reaction to the worker pullingthe pull cable. When a worker pulls the pull cable, a portion of thepull cable is deflected, which results in a linear displacement of theend of the pull cable coupled to the cable pull switch. When the lineardeflection at the cable pull switch exceeds a threshold, the contactblocks become activated (e.g., with snap action) and the emergency stopis implemented. Additionally, many cable pull switches protect againstpull cable failure by implementing an emergency stop if the pull cableenters a slack condition (e.g., not enough tension exerted by the pullcable on the switch) or a cut condition (no tension on the cable andnone at the switch). To implement this, existing pull switches may havea second mechanical contact block that becomes activated when the lineardisplacement of the end of the cable connected to the pull cable isreduced by action of a tensioning spring within the cable pull switch asthe cable enters the slack or cut condition, or utilize an unstablesystem where too much or too little tension causes a mechanism toactuate the contact block.

The linear physical positions of the activation points of the contactblocks and mechanism dictate the thresholds of operation of the cablepull switch. These thresholds are not easily altered, and thereforerequire careful adjustment of the tension of the pull cable duringoperation and repeated checks and adjustments over the lifetime of thepull cable installation (for example, as the cable stretches to generateslack or as the temperature changes in a particular applicationsetting). Existing cable pull switches utilize a mark on the movableportion of the cable pull switch (e.g., a shaft connected to the pullcable), which is then compared to a mark on the cable pull switch bodyto determine if a length of the pull cable is adjusted such that theproper tension is exerted on the pull cable by the cable pull switch.The tension of the pull cable is often adjusted with one or moreturnbuckles or with a cable tensioning system. Though suitable for atleast some purposes, such approaches do not necessarily meet all needsof all application settings and/or all users. For example, a technicianinstalling or adjusting the tension on the pull cable may have to adjustelements that are located a distance from the cable pull switch (e.g.,25 meters or more), in which case the technician (e.g., if workingalone) would have to iteratively walk between the adjustment locationand the cable pull switch to properly adjust the tension.

Further, because the positions of the activation points of the contactblocks dictate the thresholds of operation of the cable pull switch,tension on the pull cable may have to be adjusted more often to accountfor thermal expansion/contraction. The thresholds are often fairly closetogether to allow for easy detection of a pull on the cable, therebycreating a safer environment. However, the close threshold may create afalse trigger situation if the pull cable were to expand or contact dueto thermal changes.

Additionally, present cable pull switches are susceptible to jamming orother conditions rendering the cable pull switch incapable ofregistering a cable pull event. For example, a shaft of the cable pullswitch may become deformed or damaged or the cable may become pinched.Present systems are unable to detect a jamming situation until a userpulls on the cable. Accordingly, technicians or other maintenance creware required to perform routine checking of pull cable systems to ensureproper operation and to ensure that a previously undetected physicaldeformity in the cable pull system has not rendered the systeminoperable.

Additionally, existing cable pull switches are binary in operation, bothin their output signal and in their method of detection. Accordingly,existing cable pull switches lack a dynamic response to environmentaland situational changes and are therefore limited in their flexibilityand application.

SUMMARY

In one embodiment, a cable pull switch is described. The cable pullswitch comprises a polychotomous cable pull sensor configured to providea reading comprising at least one of a plurality of values, the readingcorresponding to at least one of a tension on a pull cable or a lineardisplacement of a first end of a pull cable, and at least one processorcoupled to the polychotomous cable pull sensor. The processor configuredto determine a rate of change of the value of the reading from thesensor, and determine an occurrence of a cable pull event, thedetermination based at least in part on the determined rate of change ofthe value. The at least one processor of the cable pull switch mayfurther determine whether the rate of change of the value of anelectrical resistance through the polychotomous cable pull sensor isbelow a threshold rate of change value, and adjust an upper pullthreshold value to a new upper pull threshold value that is based on apresent reading of the value of the electrical resistance through thestrain gauge. The at least one processor of the cable pull switch mayfurther determine whether the reading is below a lower slack thresholdvalue, the lower slack threshold value indicative of a cable slackevent, and generate an output signal indicative of the cable slack eventin response to determining that the reading is below the lower slackthreshold value.

In another embodiment, a cable pull switch is described. The cable pullswitch comprising a polychotomous cable pull sensor configured toprovide a reading comprising at least one of a plurality of values, thereading corresponding to at least one of a tension on a pull cable or alinear displacement of a first end of a pull cable. The cable pullswitch further comprising at least one processing device coupled to thecable pull sensor. The processing device configured to receive thereading the cable pull sensor; determine whether a value of the readingis outside of a non-tripped value window, a first limit edge side of thenon-tripped value window comprising a pull threshold value, the pullthreshold value being indicative of a cable pull event; and generate anoutput signal indicative of the cable pull event in response todetermining that the value of the reading is outside of the non-trippedvalue window on the first limit edge side. The at least one processingdevice may be further configured to determine whether the value of thereading is outside of the non-tripped value window, a second limit edgeside of the non-tripped value window comprising a slack threshold, theslack threshold indicative of a cable slack event, and generate anoutput signal indicative of the cable slack event in response todetermining that the value of the reading is outside of the non-trippedvalue window on the second limit edge side. The at least one processingdevice may be further configured to determine whether the reading isbelow a lower slack threshold value, the lower slack threshold valueindicative of a cable slack event, and generate an output signalindicative of the cable slack event in response to determining that thereading is below the lower slack threshold value.

In another embodiment, a cable pull switch is described. The cable pullswitch comprising a polychotomous cable pull sensor configured toprovide a reading comprising at least one of a plurality of values, thereading corresponding to at least one of a tension on a pull cable or alinear displacement of a first end of a pull cable. The cable pullswitch further comprising at least one processor coupled to the cablepull sensor. The processor configured to determine a rate of change ofthe value of the reading from the sensor, determine whether a rate ofchange of the reading is outside of a non-tripped value window, a firstlimit edge side of the non-tripped value window comprising a thresholdvalue, the pull threshold value being indicative of a cable pull event,and determine an occurrence of a cable pull event based on determiningthat rate of change of the value of the reading is outside of thenon-tripped value window on the first limit edge side. The at least oneprocessor may be further configured to determine whether the value ofthe reading is outside of the non-tripped value window, a second limitedge side of the non-tripped value window comprising a slack threshold,the slack threshold indicative of a cable slack event, and generate anoutput signal indicative of the cable slack event in response todetermining that the value of the reading is outside of the non-trippedvalue window on the second limit edge side. The at least one processormay be further configured to determine whether the value of the lineardisplacement is outside of the non-tripped value window on the firstlimit edge side by determining whether the value of displacement exceedsthe pull threshold value.

In another embodiment, a cable pull switch is described. The cable pullswitch comprising a polychotomous cable pull sensor configured toprovide a reading comprising at least one of a plurality of values, thereading corresponding to at least one of a tension on a pull cable or alinear displacement of a first end of a pull cable. The cable pullswitch further comprising at least one processor coupled to thepolychotomous cable pull sensor. The processor configured tocontinuously monitor the reading; determine a rate of change of thevalue of the reading from the sensor; periodically adjust an upper pullthreshold value at a fixed interval of time if the rate of change of thevalue of the reading from the sensor is below a rate of changethreshold; periodically adjust a lower slack threshold value at thefixed interval of time if the rate of change of the value of the readingfrom the sensor is below a rate of change threshold; and determine anoccurrence of a cable pull event, the determination based at least inpart on the determined rate of change of the value.

In another embodiment, an apparatus comprising a cable pull switch isdescribed. The cable pull switch including a substrate configured tocouple to a first end of a pull cable and configured to experience avariable mechanical stress related to a tension exerted by the pullcable. The cable pull switch further includes an electrical strain gaugebonded to the substrate and configured to alter an electrical resistancethrough the strain gauge in proportion to the variable mechanical stressexperienced by the substrate; and at least one processing device coupledto the strain gauge. The processing device configured to receive anindication of the value of the electrical resistance through the straingauge; determine whether the value of the electrical resistance throughthe strain gauge exceeds an upper pull threshold value, the upper pullthreshold value being indicative of a cable pull event; and generate anoutput signal indicative of the cable pull event in response todetermining that the electrical resistance through the strain gaugeexceeds the upper pull threshold value. The cable pull switch mayfurther include a spring loaded shaft coupled to the substrate, thespring loaded shaft configured to be coupled to the pull cable and toslide along a longitudinal axis of the shaft to translate a tensionexerted by the pull cable to the substrate. The substrate may be a metalsubstrate.

In a further embodiment, an apparatus comprising a cable pull switchconfigured to be coupled to a first end of a pull cable is described.The cable pull switch comprising a linear optical sensor arrayconfigured to measure a linear displacement of the first end of a pullcable. The cable pull switch further comprises at least one processingdevice coupled to the linear optical sensor array. The processing deviceconfigured to receive from the linear optical sensor array a signalindicative of the value of displacement of the first end of the pullcable; determine whether the value of displacement is outside of anon-tripped value window on a first side of the non-tripped value windowdefined by a pull threshold value, the pull threshold value beingindicative of a cable pull event; and generate an output signalindicative of the cable pull event in response to determining that thevalue of displacement is outside of the non-tripped value window on thefirst side.

In a further embodiment, a cable pull switch is described. The cablepull switch comprising a spring configured to couple to a first end of apull cable and configured to at least one of linearly compress orlinearly expand in relation to a linear displacement of the first end ofthe pull cable. The cable pull switch further comprising an electricalinductance sensor electrically coupled to the spring and configured tosense an electrical inductance value of the spring and to sense a changein the electrical inductance value of the spring in relationship to atleast one of a linear compression or a linear expansion of the spring,and at least one processing device coupled to the electrical inductancesensor. The at least one processing device configured to receive fromthe electrical inductance sensor a signal indicative of the electricalinductance value of the spring; determine whether the electricalinductance value is outside of a non-tripped value window on a firstside of the non-tripped value window defined by a pull threshold value,the pull threshold value being indicative of a cable pull event; andgenerate an output signal indicative of the cable pull event in responseto determining that the electrical inductance value is outside of thenon-tripped value window on the first side.

In another embodiment, a cable pull switch is described. The cable pullswitch comprising an illuminator configured to output a visualindication corresponding to a requirement to at least one of increase ordecrease the tension exerted by a pull cable coupled to the cable pullswitch while in a pull cable tension adjustment state.

In further embodiment, a system is described. The system comprising acable pull switch configured to couple to a first end of a pull cable.The system further comprising a pull cable excitation module configuredto couple to a second end of the pull cable; enter a pull cableexcitation state by varying a tension exerted on the second end of thepull cable; and communicate with the cable pull switch to initiate thepull cable excitation state. Wherein the cable pull switch is furtherconfigured to detect at the first end of the pull cable the carryingtension exerted on the second end of the pull cable during the pullcable excitation state; and generate an output signal indicative of apull cable failure in response to failing to detect the varying tensionduring the pull cable excitation state.

These and other benefits may become clearer upon making a thoroughreview and study of the following detailed description. Further, whilethe embodiments discussed above a listed as individual embodiment, it isto be understood that the above embodiments, including all elementscontained therein, can be combined in whole or in part.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an example contextual implementation of acable pull system in accordance with various embodiments;

FIG. 2 shows a cable pull switch in accordance with various embodiments;

FIG. 3 shows an example strain gauge assembly as an example of apolychotomous sensor in accordance with various embodiments;

FIGS. 4A and 4B show example implementations of a polychotomous sensorusable with the cable pull switch of FIG. 2 in accordance with variousembodiments;

FIG. 5 shows an example inductance sensor as an example of apolychotomous sensor in accordance with various embodiments;

FIG. 6 shows another example implementation of a polychotomous sensorusable with the cable pull switch of FIG. 2 in accordance with variousembodiments;

FIG. 7 shows an example linear optical sensor assembly as an example ofa polychotomous sensor in accordance with various embodiments;

FIG. 8 shows another example implementation of a polychotomous sensorusable with the cable pull switch of FIG. 2 in accordance with variousembodiments;

FIG. 9 illustrates various operational aspects of the cable pull switchof FIG. 2 in accordance with various embodiments;

FIG. 10 illustrates various other operational features of the cable pullswitch of FIG. 2 in accordance with various embodiments;

FIG. 11 illustrates yet other operational features of the cable pullswitch of FIG. 2 in accordance with various embodiments;

FIG. 12 shows an example state table of operational states of the cablepull switch of FIG. 2 in accordance with various embodiments;

FIG. 13 shows a pull cable excitation module 1300 in accordance withvarious embodiments; and

FIG. 14 shows a cable pull system illustrating functional aspects of thepull cable excitation module 1300 in accordance with variousembodiments.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and/or relative positioningof some of the elements in the figures may be exaggerated relative toother elements to help to improve understanding of various embodimentsof the present invention. Also, common but well-understood elements thatare useful or necessary in a commercially feasible embodiment are oftennot depicted in order to facilitate a less obstructed view of thesevarious embodiments. It will further be appreciated that certain actionsand/or steps may be described or depicted in a particular order ofoccurrence while those skilled in the art will understand that suchspecificity with respect to sequence is not actually required. It willalso be understood that the terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above, exceptwhere different specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

Referring now to the figures, FIG. 1 illustrates an example contextualimplementation of a cable pull system 100 in accordance with variousembodiments. The cable pull system 100 includes a first cable pullswitch 102, an optional second cable pull switch 104, a pull cable 106extending between the switches, and an optional tensioner 108 installedalong the pull cable 106.

In prior art application settings, the cable pull switches 102, 104 maybe of any suitable contact-based design, for example, as is described inU.S. Pat. No. 6,365,850 to Arnold et al., the contents of which areincorporated by reference. The cable pull switches 102 and 104 may eachcomprise a tension indicator 110, an emergency stop button 112, and areset knob 114. Each cable pull switch 102, 104 may also comprise atubular body extension 116 which receives a spring-loaded shaft 118(shown in phantom) attached to a rotatable D-ring connector 120. Theswitches are mounted such that the distance between the D-ring connector120 is generally less than 100 meters, though other distances may besuitable in various application settings.

In various embodiments, the pull cable 106 can be a PVC coated steelcable, although any suitable cable may be used. The pull cable 106 maybe attached between the cable pull switches 102, 104 by passing thecable around suitable thimbles looped through the D-ring connector 120and clamping the cable ends in clamps 122, in a known manner. The pullcable 106 is typically supported along its length by means of aplurality of eye bolts 124 placed at distances of 2 to 3 meters apartalong the machinery.

Turning now to FIG. 2, an improved cable pull switch 200 is illustratedin accordance with various embodiments. Like the cable pull switch 102of FIG. 1, the cable pull switch 200 includes a housing 202 and mayinclude a tubular body extension 204 (similar to or the same as tubularbody extension 116 discussed above) through which a shaft 206 passes,however, the tubular body extension 204 is not required in allembodiments. A rotatable D-ring 208 connector 208 can also be includedat a distal end of the shaft 206 to allow a pull cable 106 to beconnected thereto. In various embodiments, a spring 210 is includedwithin the tubular body extension 204 or within the housing 202 and isconfigured to exert a rearward force on the shaft 206 toward the housing202. The spring 210 may be a compression spring that is compressed whenthe shaft 206 is displaced in a direction away from the housing 202, forexample, as is shown in FIG. 2. Such displacement may occur during acable pull event. In other embodiments, the spring 210 may be anextension spring and may be configured to extend when the shaft 206 isdisplaced in a direction away from the housing 202. Other spring typesand configurations may be possible.

The cable pull switch 200 can include a sensor 212, and in someembodiments, can also include a processing device 214, a communicationmodule 216, an indicator 218, and/or an emergency stop (“e-stop”)actuator 220. In various embodiments, the sensor 212 is a polychotomoussensor, in that the sensor 212 provides a variable output reading thatis not limited to a binary on/off or open/closed state (e.g., unlike acontact switch, which can only provide an open or closed output). Theoutput of the polychotomous sensor 212 may be digital or analog, and mayinclude a plurality of possible values (possible near infinite outputvalues if analog). The polychotomous sensor 212 may output one of theplurality of possible values dependent upon the sensed condition, whichoutput value may be always available (e.g., when operating),continuously updated, or only available or updated upon request (e.g., arequest from processing device 214 or another processing device). Invarious embodiments, the sensor 212 is an electrical sensor and mayinclude various circuitry elements and modules to affect its particularsensing mechanism. Examples of polychotomous sensors 212 include, butare not limited to, strain gauges, linear optical sensor arrays, orinductance sensors, all of which are discussed in greater detail below.Still further examples may include Hall effect sensors, proximitysensors, potentiometric position sensors, capacitive position sensors,linear voltage differential transformers, magnetostrictive linearposition sensors, eddy current-based position sensors, fiber-opticposition sensors, rotary encoders, incremental encoders, wire drawencoders, gravimeter sensors, gyroscopic sensors, impact sensors,inclinometers, laser rangefinder sensors, selsyn sensors, shockdetectors, tilt sensors, ultrasonic thickness gauges, variablereluctance sensors, bhangmeter sensors, hydrometer sensors, forcesensors, level sensors, load cells, magnetic level gauges, nucleardensity gauges, piezoelectric sensors, torque sensors, viscometersensors, and other known and unknown sensing devices that are capable ofoutputting a plurality of sensor values corresponding to a measurementof a strain, a stress, a tension, a location, a velocity, anacceleration, a change in a condition, or other measurable conditions.The polychotomous sensor 212 may be configured to output an absolutevalue (e.g., an actual position of one element compared to another, or ameasured value of a strain exerted on an object, etc.) or an incrementalvalue (e.g., a position relative to an end stop position or relative toa position at startup, etc.).

The processing device 214 may communicate with the sensor 212 and/or thecommunication module 216 via any known communication protocol.Alternatively, either or both of the sensor 212 and the communicationmodule 216 may be integral with the processing device 214. Theprocessing device 214 may comprise one or more microprocessors,microcontrollers, Field-Programmable Gate Arrays (FPGA),Application-Specific Integrated Circuits (ASIC), Digital SignalProcessors (DSP), Peripheral Interface Controllers (PIC) processors, orother known processing device types or combinations thereof. Theprocessing device 214 may, in certain embodiments, include or be coupledto memory devices as are known in the art. The processing device 214 maybe configured to execute code (e.g., firmware or software) that may bestored therein or stored on a separate communicatively coupled memorydevice. The code may be loaded for the processing device 214 to executethrough the communication module 216 (e.g., at manufacture time orduring an upgrade), or may be preloaded during manufacture and/orassembly through another process. The communication module 216 (whethera separate module or integral with the processing device 214) isconfigured to output one or more signals (e.g., an Output SignalSwitching Device signal (“OSSD”)) through a communication port 222. Theoutput signal may be coupled to one or more communication relays orother devices to effect control of an associated machine, particularlyto shut the machine off or enter a safe mode in the event that theoutput signal indicates a trigger condition has occurred (e.g., a cablepull event). The communication module 216 may also receive inboundcommunications from other sources (e.g., from a network of devices orfrom the associated machine). Alternatively, in the absence of aprocessing device 214, the cable pull switch 200 may provide the sensorvalues from the sensor 212 to the output port 222 in a known manner sothat a separate communicatively linked device can receive the sensorvalues and make decisions based thereon. In such an approach, thecommunication module 216 or a different processing device may beincluded, for example, a less powerful microprocessor, to effectcommunication through the port 222 of the sensor values.

In some embodiments, the cable pull switch 200 includes the e-stopactuator 220, which may be, for example, a highly-visible button locatedon an accessible surface (e.g., top surface) of the housing 202 suchthat the actuator 220 can be easily depressed. The e-stop actuator 220may utilize the same technologies described herein (for sensing a cablepull event through the shaft 206) to sense an actuation or depression ofthe actuator 220, or the actuator 220 may use different technology(e.g., more primitive contact-based switching) to sense actuation. Insome embodiments, the e-stop actuator 220 is communicatively coupled tothe processing device 214 and, upon actuation, will affect an outputsignal through the port 222 indicative of its actuation to affectstoppage of the associated machinery or to serve another function. Theoutput function of the e-stop actuator 220 may serve the same functionas that of the cable pull sensing function (e.g., to stop an associatedmachine), or may be a different function altogether (e.g., to stop adifferent machine).

Turning now to FIGS. 3 and 4A, an example implementation of apolychotomous sensor 212 within the cable pull switch 200 is illustratedin accordance with various embodiments. In this approach, a strain gaugeassembly 300 includes a substrate 302 and a strain gauge 304 bonded to asurface of the substrate 302. The substrate 302 may be formed of metal(e.g., steel), though other rigid materials may be utilized. Thesubstrate 302 may include a member 306 configured to receive stresses.The member 306 may also include one or more holes 308 and/or one or moretabs 310 to allow attachment to other elements. The strain gauge 304 maybe a known type of strain gauge (e.g., using a metallic foil pattern, asemiconductor strain gauge, or other known and currently unknown straingauge types) which may utilize a traditional Wheatstone bridge (or otherknown or currently unknown circuit designs) to implement an outputreading. The strain gauge 304 may be bonded to a surface of thesubstrate 302 through any known mechanical bonding technique, includingbut not limited to adhesives (e.g., epoxy) or thermal bonding. Manyvariations are possible as to the design and implementation of thestrain gauge 304 and the substrate 302 and may be application specific.

The strain gauge 304 may include electrical wiring 312 to output asensed value. For example, the strain gauge 304 may output or makeavailable a value of an electrical resistance through the strain gauge304. This value can be coupled, via the electrical wiring 312, to ananalog-to-digital converter (ADC) 314 which may be separate from orintegral with the processing device 214. The ADC 314 may convert areading of the electrical resistance through the strain gauge 304 into adigital value for use by the processing device 214 or another device.For example, the ADC 314 (or another device) may effect a voltage orcurrent to flow through the strain gauge 314 and a value of theelectrical resistance can be determined by reading a correspondingcurrent or voltage output (e.g., according to the equation V=I*R oranother variation, where V is the voltage, I is the current, and R isthe resistance). Alternatively, the strain gauge 304 itself may beconfigured to output a digital value of the electrical resistance by anincorporated ADC within the strain gauge 304.

As a force or stress (e.g., a bending stress) is exerted upon the member306 of the substrate 302, the member 306 will flex slightly inproportion to the amount of stress exerted. In accordance with variousembodiments, this slight flexing causes a corresponding and proportionalflexing in traces of a resistive circuit within the strain gauge 304,which in turn alters a value of the electrical resistance there through.The value of this electrical resistance is therefore related to andproportionate to the amount of stress exerted upon the member 306 of thesubstrate 302.

Turning now to FIG. 4A, an example implementation of the strain gaugeassembly 300 with the cable pull switch 200 is illustrated in accordancewith various embodiments. In one approach, the strain gauge assembly 300can be located within the tubular body extension 204 (e.g., with notchesor ridges formed therein, or the like) such that the shaft 206 passesthrough the hole 308 of the substrate 302. Other arrangements and/orconfigurations are possible, such as where the tubular body extension204 is eliminated or reduced in size such that the spring 210 is atleast partially external to the housing 202 (see FIG. 4B). In thisarrangement, the spring 210 can be at least partially or completely freeof mechanical interference with the tubular body extension 204. Themember 306 of the substrate 302 is free from mechanical interferencefrom adjacent side walls (e.g., the front wall surface 402) such that itis allowed to flex. Wiring 312 (not shown in FIGS. 4A and 4B) can berouted from the strain gauge 304 to a processing device 214 or otherelement. A stop element 404 (e.g., a ring or pin) can be secured to orintegrally formed with the shaft 206. In one embodiment, the stopelement 404 (or another feature of the shaft 206) may engage a rearbackstop 406 in the absence of a tension force (FT) that exceeds theforce exerted by the spring 210. By this, the rear backstop 406 dictatesa fully contracted resting position of the shaft 206. Other positionsand/or configurations are possible for the rear backstop 406.

The spring 210 (here, a compression spring) is compressed between thestop element 404 and the member 306 of the substrate 302 of the straingauge assembly 300. In this manner, a tension force (FT) exerted on theshaft 206 in the longitudinal direction (indicated by the arrow FT) bytension from the pull cable 106 will compress the spring 210, therebyexerting a stress on the substrate 302. As the shaft moves furtheroutward (e.g., by a cable pull event or by increased tension adjustmentof the pull cable 106), the spring 210 is compressed further, whichincreases the force exerted by the spring 210 on the substrate 302resulting in increased stress exerted on the substrate 302. This stressexerted on the substrate 302 by spring 210 is directly related to thedisplacement of the shaft 206 (i.e., in a non-moving state) by Hooke'sLaw (F=−k*X, where F is the force exerted by the spring 210, k is thespring constant of the spring 210, and X is the displacement (e.g.,compression) of the spring 210 from its non-compressed restingposition). By measuring the stress in the substrate 302 with the straingauge 304, and with the knowledge of other variables (e.g., the designedspring constant k of the spring 210), the displacement distance of theshaft 206 can be determined. This calculated displacement distance, or,alternatively, the measured stress value itself, can be used to detect acable pull event, a cable slack event, or to determine a properadjustment tension (e.g., during installation and/or maintenanceadjustment).

Other variations are possible for the placement of the strain gaugeassembly 300 and/or its interaction with spring 210 or a differentspring (e.g., an extension spring or a spring purposed solely forsensing purposes) or with the shaft 206 itself. For example, the straingauge assembly 300 and/or the spring 210 (or a different spring) may beplaced within the housing 202 rather than within the tubular bodyextension 204. Further, many variations on the design of the substrate302 and its interaction with the spring 210 and/or shaft 206 may bepossible and are contemplated by this disclosure.

Turning now to FIG. 5, a different implementation of a polychotomoussensor 212 is illustrated in accordance with various embodiments. FIG. 5illustrates a conceptual implementation of an inductance sensor 502 inaccordance with various embodiments. The inductance sensor 502 isconnected to the spring 210 (or another spring), possibly throughvarious interceding and/or conditioning circuitry elements 504 as may beappropriate in a given application setting. For example, two leads areprovided from the inductance sensor 502 and/or circuitry elements 504,one lead is electrically connected to a first end of the spring 210(e.g., a coil spring), and the second lead is electrically connected toa second end of the spring 210. The inductance sensor 502 can thenmeasure an inductance of the spring 210. As the spring is compressed orexpanded (shown by arrow 506), the inductance of the spring 210 canchange, and the inductance sensor 502 can sense and measure thosechanges. One example of an inductance sensor 502 may include a LDC1000manufactured by Texas Instruments® of Dallas, Tex.

The electrical inductance of the spring 210 may be proportional to thecompression distance of the spring 210, which compression distance isdirectly proportional to the displacement distance of the shaft 206. Assuch, the inductance sensor 502 can measure the electrical inductancewithin the spring 210 and a processing device 214 (or another device)can convert that electrical inductance value into a displacementdistance and/or a tension force value.

Turning to FIG. 6, an example cable pull switch 600 incorporating theinductive sensor 502 is illustrated in accordance with variousembodiments. The inductance sensor 502 may be electrically coupled tothe ends of the spring 210 through leads (shown in dashed line passingthrough the shaft 206, however their actual routes through the assemblymay be different). In this approach, the inductance sensor 502 canmeasure the inductance through the spring 210 operating as a maintensioning spring. Alternatively, and in accordance with a differentembodiment, a second spring 602 different from the spring 210 could beprovided elsewhere (e.g., within the housing 202) such that the secondspring 602 is compressed and/or expanded in relation to the displacementof the shaft 206. Each end of the second spring 602 could be connectedto the inductive sensor 502 and the value of the electrical inductancethrough the second spring 602 could be used to determine a shaftdisplacement distance and/or tension.

Accordingly, the processing device 214 can monitor the presentdisplacement distance of the shaft 206 and any changes in thatdisplacement distance via the inductance sensor 502 in order to detect acable pull event, a cable slack event, or to aid in tensioningadjustments. Similarly, an inductance sensor 502 could be utilized withthe e-stop actuator 220 to detect a depressed distance of the actuator220 to detect its actuation.

Turning now to FIG. 7, a different implementation of a polychotomoussensor 212 is illustrated in accordance with various embodiments. FIG. 7illustrates a conceptual implementation of linear optical sensorassembly 700 in accordance with various embodiments. The linear opticalsensor assembly 700 includes a linear optical sensor 702, an illuminator(e.g., an infra-red light emitting diode (IR LED) 704, and a movabletarget 706. The linear optical sensor array 702 (and the IR LED 704) canbe electrically coupled to the processing device 214 to controloperations thereof and to receive optical position readings therefrom.In various approaches, a clock signal (CLK) and a serial input signal(SI) (to initiate data readout) may be provided from the processingdevice 214 to the linear optical sensor array 702 and an analog ordigital output signal from the linear optical sensor array 702 may becoupled back to the processing device 214 or to an interceding ADC, ifrequired (not shown). In operation, and in accordance with variousembodiments, the IR LED 704 provides light 708 to illuminate a sensorsurface the sensor array 702 including a plurality of individualphotodiode sensors. The target 706 may include one or more apertures 710and/or light blocking elements 712. Light passes through the apertures710 and onto illuminated portions 714 of the sensor surface of thesensor array 702, while other shaded portions 716 of the sensor surfaceare shaded from the light 708 by the light blocking elements 712. Inthis manner, a location of the target 706 relative to the linear opticalsensor array 702 can be determined based on the encoded pattern of light714 and shade 716 sensed by the individual photodiodes of the sensorarray 702.

Other variations are possible for the optical sensor assembly 300. Forexample, instead of apertures 710 and light blocking elements 712,reflective and non-reflective surfaces can be used. Many other knownconfigurations are possible and are contemplated by this disclosure.Additionally, the target 706 can include an encoded pattern that isabsolute or incremental, though an absolute position encoded pattern maybe beneficial in many application settings (e.g., to reduce the need foror eliminate a calibration step upon power up).

Turning to FIG. 8, an example cable pull switch 800 incorporating thelinear optical sensor assembly 700 is illustrated in accordance withvarious embodiments. The linear optical sensor assembly 700 may beincluded within the housing 202 of the cable pull switch 800. The target706 may be coupled directly (as shown) or indirectly to the shaft 206such that linear movement of the shaft 206 corresponds to linearmovement of the target 706. The light pattern created by the target 706and illuminated onto the sensor surface of the optical sensor array 702provides information as to the present displacement distance of theshaft 206. The optical sensor array 702 can in turn provide the sensedoptical position data to the processing device 214, which can in turndetermine the present displacement distance of the shaft 206. As thetarget 706 moves in connection with movement of the shaft 206, the lightpattern illuminated on the sensor surface of the optical sensor array702 will change and the corresponding optical position data will change.

Accordingly, the processing device 214 can monitor the presentdisplacement distance of the shaft 206 and any changes in thatdisplacement distance via the linear optical sensor assembly 300 inorder to detect a cable pull event, a cable slack event, or to aid intensioning adjustments. Similarly, a linear optical sensor assembly 300could be utilized with the e-stop actuator 220 to detect a depresseddistance of the actuator 220 to detect its actuation.

In various ones of the above embodiments (e.g., the strain gaugeembodiment, the inductance sensor embodiment, and/or the optical lightsensor array embodiment) or other possible embodiments, the particularsensor 212 type used may be an absolute sensor or an incremental sensor.In either approach, it may be beneficial to calibrate the readings fromthe sensor 212. For example, springs 210 and or sensors 212 may havetolerances in their initial manufacturing such that calibration couldhelp ensure proper correlation of values to positions and/or tensionamounts. If a strain gauge assembly 300 is used, an initial strain valuereading could be taken during assembly of the strain exerted on thesubstrate 302 by the spring 210 when the shaft 206 is in its fullycontracted resting position. Optionally, a second strain value readingcould be taken at a known and controlled displacement distance, whileadditional different readings could be taken in a similar manner aswell. A correlation could be made between the recorded strain value(s)and the displacement distance(s) (e.g., zero and/or another knowndisplacement distance) to calibrate the cable pull switch 200. Thecalibration reading(s) could also be made periodically or with everypower-up to account for any deterioration or change in the strength ofthe spring 210 and/or the substrate 302 (e.g., due to use over timeand/or due to thermal changes) or other factors.

Similarly, if an inductance sensor 502 is used, an initial inductancevalue reading could be taken when assembled or when installed at one ormore known displacement positions to calibrate the cable pull switch200. Again, these calibration readings could be repeated periodically aswell.

If a linear optical sensor assembly 700 is used, initial opticalposition value readings could be taken when assembled or when installedat one or more known displacement positions to calibrate the cable pullsswitch 200. However, the variations of a linear optical sensor array 702and/or a moving target within the cable pull switch 200 may be much morecontrollable. As such, variations in the optical position value readingsmay be negligible so as to negate the need for calibration.Alternatively, a single optical position value reading can be made whilethe shaft 206 is in the fully contracted resting position, which couldbe used as the zero-displacement point and could be used whether thelinear optical sensor assembly 700 is an absolute position sensor or anincremental position sensor.

Additionally still, these disclosed embodiments may enable calibrationof the system as a whole to account for variations in, for example, thespring 210. A calibration step could be utilized during assembly toexert a calibrated tension force (FT) (e.g., an ideal center tensionforce) on the shaft 206, wherein the particular sensor 212 used canrecord that value (e.g., measured strain/tension and/or displacementdistance) as a calibrated value for the ideal center tension force.

These are but a few examples of implementation of polychotomous sensortypes within a cable pull switch 200. Many other sensor types may beutilized that provide data or readings beyond the simple on/off oropen/closed status of contact switches. As is made apparent, theversatility of a polychotomous sensor and the additional data itprovides can be useful to implement a bevy of features and/orimprovements.

Turning now to FIG. 9, various operational aspects of the improved cablepull switch 200 are illustrated in accordance with various embodiments.Shown here is a graph of a sensed value (Y-axis) over time (X-axis). Thesensed value may be a strain value (e.g., corresponding to a tensionforce FT exerted on the cable pull switch) or a displacement value(e.g., corresponding to the displacement distance of the shaft 206). Forexample, the sensed value may be a value of the electrical resistancethrough a strain gauge 304, which corresponds to a strain or tensionexerted by the pull cable 106. The sensed value may be a value of theelectrical inductance as measured by an inductance sensor 502, which maycorrespond to a displacement distance of the end of the pull cable 106.Similarly, the sensed value may be a value of displacement from a linearoptical sensor array 702, which may correspond to a displacementdistance of the end of the pull cable 106. In various embodiments, thevalues (e.g., strain/tension and/or displacement distance) may beproportional (e.g., linearly proportionate), for example, according toHooke's law for springs.

A non-tripped value window 902 is illustrated including a pull thresholdvalue 904 defining a first side of the window 902 and a slack thresholdvalue 906 defining a second side of the window 902. When the value ofthe tension or displacement is within the non-tripped value window 902(e.g., after a reset or initialization), the cable pull switch 200effects an output indicative of a non-tripped condition. Here, as isshown initially, an Output Signal Switching Device (OSSD) output (e.g.,as may be output from the cable pull switch 200 via the port 222) ishigh when the sensed value is within the non-tripped value window 902,indicating an absence of a trip condition (e.g., the absence of a cablepull event or a slack event).

The sensed value may be relatively steady and unchanging at a settension or displacement distance (e.g., corresponding to the set tensionfor the system). However, upon a cable pull event, the tension and/ordisplacement distance may increase, typically rapidly, as a user grabsand yanks on the pull cable 106. This is illustrated as the upward spikein tension or displacement. As the tension or displacement increases, itwill exceed the pull threshold value 904 such that the sensed value isoutside of the non-tripped value window 902 on its first side (e.g.,exceeds the pull threshold value 904). At this point, a processingdevice 214 will determine the occurrence of a cable pull event and willgenerate an output signal indicative of the same. As is shown here, theOSSD signal goes from a high state to a low state, indicating a cablepull event.

FIG. 9 also illustrates a cable slack event. After the occurrence of thecable pull event, a reset may take place to reset the OSSD signal to anon-tripped high state (though, a cable slack event can occur at anytime). A cable slack event may occur, for example, in an instance wherethe pull cable 106 may be cut, a cable clamp 122 may have slipped, acable tensioner 108 may have failed, or thermal expansion caused thepull cable 106 to expand such that the tension or displacement droppedbelow a slack threshold value 906. In such an instance, the sensedtension or displacement value may fall below the slack threshold value906 such that the sensed value is outside of the non-tripped valuewindow 902 on its second side. At this point, the processing device 214can determine the occurrence of a cable slack event and can generate anoutput signal indicative of the same. As is shown here, the OSSD signalgoes from a high state to a low state, indicating a cable slack event.

Many other variations are possible. For example, separate or multipleoutput signals may be provided for each condition and additional datamay be output as to, for example, the highest/lowest sensed value, arate of change of the value, or other data. This data may be used by,for example, a system management computer or other device. Also,although the pull threshold value 904 is shown as greater than the slackthreshold value 906 (as would correspond to actual tensions on the pullcable 106 or displacement distance of the shaft 206), variouspolychotomous sensors 214 may be configured so that increasing tensionon the pull cable 106 results in a decreased sensed value. In such areversed approach, the first side of the non-tripped value window 902would be the lower end defined by the pull threshold value 904 and thesecond side of the non-tripped value window 904 would be the upper endand defined by the slack threshold value 906.

Turning now to FIG. 10, optional features of the cable pull switch 200are illustrated in accordance with various embodiments. Like thenon-tripped value window 902 (also shown in FIG. 10), an adjustmentvalue window 1002 may also exist. This adjustment value window 1002 maybe narrower than the non-tripped value window 902 and may be defined ona first side by a pull adjustment margin threshold value 1004representing a value that is within the non-tripped value window 902 bya margin from the pull threshold value 904. For example, in aconfiguration where the pull threshold value 904 is greater than theslack threshold value 906 (as is shown in FIGS. 9 and 10), the pulladjustment margin threshold value 1004 is an upper pull adjustmentmargin threshold value 1004 and is less than the pull threshold value904. Similarly, the adjustment value window 1002 may be defined on asecond side by a slack adjustment margin threshold value 1006representing a value that is within the non-tripped value window 902 bya margin from the slack threshold value 906. As is shown in FIG. 10, theslack adjustment margin threshold value 1006 is a lower slack adjustmentmargin threshold value 1006 and is greater than the slack thresholdvalue 906. The adjustment value window 1002 may be useful, for example,during tension adjustment of the pull cable 106 (e.g., duringinstallation and/or maintenance) to provide a narrower window in whichthe tension of the pull cable 106 should be adjusted to keep the normaloperation tension of the pull cable 106 closer to an ideal tension thatis away from the edges of the non-tripped value window 902.Additionally, if the tension of pull cable 106 approaches the pulladjustment margin threshold value 1004 or the slack adjustment marginthreshold value 1006, the indicator 218 (see FIG. 2) may be triggered toprovide a visual or audible notification that the tension of pull cable106 requires adjustment.

However, a situation may occur in normal use where thermal expansioncauses the pull cable 106 to heat up and expand (e.g., in a warmenvironment, in use outdoors, etc.). If the tension of the pull cable106 is adjusted while the cable is cool, as the cable heats up, it willexpand slowly so as to reduce the tension and/or displacement at thecable pull switch 200. This is illustrated in the first portion (leftportion) of FIG. 10, where the strain or displacement slowly drops. Thisfirst portion of FIG. 10 is shown compressed over time and the actualexpansion of the cable may take many minutes or hours. After a time, thetension and/or displacement at the cable pull switch 200 may be near orbelow the lower slack adjustment margin threshold 1006. If thetension/displacement stays within the adjustment value window 1002, noalarm or warning should be issued. However, in certain embodiments, ifthe tension/displacement exits the adjustment value window 1002 (e.g.,by dropping below the lower slack adjustment margin threshold 1006), analarm or warning may be effected indicating adjustment may be required,however normal operation of associated machinery may continue in someembodiments. If the tension/displacement drops low enough to exit thenon-tripped value window 902 (e.g., by dropping below the slackthreshold value 906), a cable slack event would be detected and anappropriate output signal could be effected indicating the same, atwhich point associated machinery could be stopped. Similarly, if tensionof the pull cable 106 was adjusted while it was warm, as the pull cable106 cools it will contract and could cause a similar problem byincreasing the tension or displacement, possibly causing an artificialtrip situation on the upper end.

These artificial trip situations could cause frustration and reduceoperating efficiency of a manufacturing plant or factory (e.g., bycreating unnecessary down-time on a line). Further, it could causeoperators to implement work-arounds to avoid these artificial tripsituations (for example, by wrapping the pull cable around a neareyelet) to avoid thermal expansion/contraction from falsely tripping thecable pull switch 200. These work-arounds could eviscerate the purposeof the cable pull switch 200. Accordingly, to avoid frustration, reducedown-time, and avoid unsafe work-arounds, various measures can beimplemented that take advantage of the extra data provided by thepolychotomous sensor 212.

In one embodiment, the cable pull switch 200 may determine a rate ofchange (e.g., a first order derivative) of the strain or displacement.This rate of change is shown as dX/dt in FIG. 10, where X is eitherdisplacement distance or strain/tension and where t is time. The rate ofchange may correspond to velocity, in some embodiments. In oneembodiment, if the rate of change is slow enough (e.g., below athreshold rate of change value), the processing device 214 in the cablepull switch 200 may periodically adjust one or more of the thresholdvalues at a fixed interval according to a present value of the sensedvalue (e.g., strain/tension or displacement distance). For example, thethreshold rate of change value can be about 10N to about 90N over a timeperiod. In one embodiment, the time period can be one second; however,the time period can be more than one second (e.g. one minute, one hour,etc.). Alternatively, the time period can be less than one second (e.g.,one millisecond, one nanosecond, etc.), or any other time period asapplicable. In one specific embodiment, the threshold rate of changevalue can be 30N over a one second period.

The cable pull switch 200 can monitor the sensed value continuously orat predetermined timed intervals, and can adjust the threshold values tomaintain a constant pull force regardless of changes in the sensed valueso from a user perspective, the user does not have to apply a greaterpull force to trip the switch 200 as heat, wear and natural stressescause the cable tension to drop below an ideal tension over time. Afloating window 1007 can be implemented in firmware in the cable pullswitch 200 with the pull threshold value 904 and the slack thresholdvalue 906 changing over time as microprocessor 214 can continuouslymeasure the tension in the pull cable 106 and update the base tension ofeach window 1007 at a fixed interval of time. Gradual changes in tensioncan move the window up or down by adjusting the pull threshold values904 and the slack threshold values 906, bounded by a minimum tension (asa non-limiting example 10N) and a maximum pulled tension (as anon-limiting example 180N). By implementing the floating windows 1007,the pull cable switch 200 can tolerate changes to the environment but itcan still be triggered by a user.

For example, if thermal expansion were to reduce the strain/tension ordisplacement distance, and the rate of change was slow enough (e.g.,minutes, hours, or possibly so slow as to be imperceptible) so as not toconfuse the slow change in strain/tension or displacement distance witha fast change from a cable cut event or another cable failure, the cablepull switch 200 may lower the thresholds 904 and/or 906 defining thenon-trip value window 902. Similarly, the system may lower thethresholds 1004 and/or 1006 defining the adjustment value window 1002.In some embodiments, the adjustment amount may be limited by anallowable adjustment amount (as non-limiting examples, +/−25%, +/−10 mmdisplacement distance, etc.) and/or an absolute lower or upper value(e.g., a lower slack threshold value 906 cannot be less than a 10 mmdisplacement distance, etc). By this, the cable pull switch canaccommodate normal thermal expansion and contraction without falselytripping the system, as long as the tension/displacement of the pullcable 106 remains within minimum safe operating conditions (e.g., nottoo much slack so that the shaft 106 is non-responsive to a cable pullevent, and not too much tension/displacement so that a cable pull eventwould exceed the maximum tension or displacement sensing abilities ofthe cable pull switch 200). Further, in a similar manner as is discussedbelow, by lowering an upper pull threshold value 904 when thermalexpansion occurs, the likelihood that the cable pull event is actuallydetected can increase.

With continued reference to FIG. 10, the right portion of the graph(after the dashed lines, which indicates passage of time) shows a cablepull event. Like in FIG. 9, a strain/tension or a displacement distanceis increased sharply in response to a user pulling on the pull cable106. If the pull cable 106 had expanded due to thermal expansion (sothat the normal resting tension/displacement was low, possibly near orbelow a lower slack adjustment margin threshold value 1006), and if auser did not pull on the pull cable 106 with substantial force, a priorart cable pull switch 102 may not register the cable pull event as theforce or distance may not be enough to enable the mechanical contacts ofthe switch to be thrown. A similar situation may occur if the pullthreshold value 904 is not adjusted.

In accordance with one embodiment, the cable pull switch 200 (andparticularly the processing device 214) may take the rate of change(dX/dt) of the sensed value into account when determining whether acable pull event has occurred. In one approach, the cable pull switch200 may adjust 1008 (e.g., lower) the cable pull value threshold 904 toa new (e.g., lower) cable pull value threshold 1010 if the rate ofchange of the sensed value exceeds a threshold rate of change value1012. As is seen in FIG. 10, the rate of change dX/dt exceeded the rateof change threshold 1012 and the upper cable pull value threshold 904was lowered to a new threshold value 1010. Once the measuredstrain/tension or displacement exceeded the new lowered threshold value1010 at point 1014, a cable pull event was determined to have occurredand the OSSD outputs were changed to indicate the occurrence of thecable pull event.

In one embodiment, the new lowered threshold 1010 may remain in effectfor as long as the rate of change dX/dt exceeds the rate of changethreshold value 1012. In another embodiment, once the rate of changedX/dt exceeded the rate of change threshold value 1012, the new loweredthreshold 1010 may remain in effect for a set period of time (e.g., 1 or2 seconds, etc.), or, in an alternative embodiment, until the rate ofchange dX/dt became negative (as shown in FIG. 10, corresponding to arelease of the pull cable 106). In another approach, a negative rate ofchange threshold value (not shown) may be the same value (e.g., butnegative) or a different value than the rate of change threshold value1012 according to the requirements of a particular application setting.In one approach, the rate of change may be an absolute value of the rateof change (e.g., |dX/dt|) so that a negative rate of change will also“exceed” the threshold 1012.

In another approach, the system may not adjust thresholds, but maysimply look to the rate of change dX/dt to indicate the occurrence of acable pull event. For example, the system may determine whether the rateof change exceeds the rate of change threshold value 1012 for a certaintime period (e.g., 0.2 or 0.5 seconds, etc.), which may serve to filterout any unintended vibrations that may briefly increase the rate ofchange, while allowing a true cable pull event to be registered solelyby the rate of change. Many other variations are possible.

Turning now to FIG. 11, another feature of the improved cable pullswitch 200 is illustrated in accordance with various embodiments. Duringinstallation and/or maintenance, the tension/displacement of the pullcable 106 may be adjusted to be at a suitable tension/displacement. Inone approach, an indicator 218 (see FIG. 2) is provided, for example, onthe housing 202 of the cable pull switch 200. The indicator 218 may bean audible indicator (e.g., to emanate an audible tone) or a visualindicator. An example visual indicator is shown at 1102, 1104, 1106, and1108, illustrating a single visual indicator at various times duringinstallation/maintenance (reference is generally made to visualindicator 1102, but may pertain to all instances 1102, 1104, 1106, and1108 of the visual indicator 1102). The visual indicator 1102 mayinclude a first illuminator 1110 indicating a requirement to increasetension exerted on the pull cable 106, a second illuminator 1112indicating a requirement to decrease the tension exerted on the pullcable 106, and, optionally, a third illuminator 1114 indicating thetension exerted on the pull cable 106 is acceptable. The illuminators1110, 1112, and 1114 may be light emitting diodes (LEDs), though otherilluminator types may be possible. The illuminators 1110, 1112, and 1114may be differing colors according to different functions (e.g., red oryellow for the first illuminator 1110 and/or the second illuminator1112, green or blue for the third illuminator 1114, though many othervariations are possible). Further, in another embodiment, a singleilluminator is used to convey through color (e.g., red for too much/toolittle tension, green for acceptable tension) and/or blinking rate (aslow blink rate when too much/too little tension and gradually speedingup to solid illumination when adjusted to an acceptable tension amount,or vise versa) to provide similar functionality and/or statusinformation as is described below.

In operation, and in accordance with various embodiments, the visualindicator 1102 can provide an illuminated visual indication to provide auser with visual feedback of pull cable 106 tension during tensionadjustment. In one embodiment, though not every embodiment, the cablepull switch may enter a tension adjustment state wherein the visualindicator 1102 is active. However, in other embodiments, the visualindicator 1102 may provide the disclosed functionality and statusfeedback whenever the cable pull switch 200 is powered without the needto enter a tension adjustment state.

In a first operational state, as is shown with visual indicator 1102,the tension/displacement is below the slack adjustment margin thresholdvalue 1006. When in this state, the first illuminator 1110 may beilluminated (indicating a requirement to increase the tension) while thesecond illuminator 1112 and the third illuminator 1114 are dark. As thetension is increased and as the tension exceeds the slack adjustmentmargin threshold value 1006 such that it is within an acceptable range(e.g., within an adjustment value window 1002), the visual indicatorenters a second operational state shown at 1104 wherein the thirdilluminator 1114 may be illuminated (indicating an acceptable tension)while the first illuminator 1110 and the second illuminator 1112 aredark. If the tension continues to increase and exceeds the upper pulladjustment margin threshold value 1004, the visual indicator enters athird operational state shown at 1106 wherein the second illuminator1112 may be illuminated (indicating a requirement to decrease thetension) while the first illuminator 1110 and the third illuminator 1114are dark. The installer can then lower the tension until the tension isback within the adjustment value window 1002, wherein the visualindicator re-enters the second operational state as is shown at 1108,which is identical to 1104. By this, an installer can be provided with avisual indication that is viewable from a distance (e.g., possibly up to25-50 meters) so that as tension adjustments are made away from the endsof the pull cable 106 (for example, at a tensioner or a turnbuckle inthe middle of the pull cable 106), the installer is not required to makemultiple iterative trips back and forth between the cable pull switch200 and the adjustment point on the cable 106, thereby saving time andimproving convenience and usability of the cable pull switch 200.

Varying brightness and or blinking rates can be used with the multipleilluminators 1110, 1112, and 1114 to provide even more detailed feedbackto a user. For example, when the tension of the pull cable 106 is withinthe adjustment value window 1002 for acceptable tension but near thethresholds 1004 or 1006, the third illuminator 1114 may blink slowly orbe dimly illuminated, which blinking or brightness may increaseeventually to solid or full bright as the tension is adjusted to be nearthe middle of the window 1002 and/or the ideal tension value. Similareffects can be provided for the first illuminator 1110 and the secondilluminator 1112.

Turning now to FIG. 12, an example state table is provided in accordancewith various embodiments. In addition to the visual indicator 1102described above, or as part of the same visual indicator 218, a statusLED illuminator may be included on the housing 202 of the cable pullswitch 200 to provide visual indication of a present operational statusof the cable pull switch. This status LED may be the same as or separatefrom the illuminators 1112, 1114, or 1116. Similarly, the communicationport 222 may include the primary OSSD output and may include a secondauxiliary output signal (e.g., AUX). These outputs may be provided onseparate and distinct conductors or terminal pins, or may be containedwith a serial communication protocol.

Various example states are shown in FIG. 12 in accordance with variousembodiments. However, one of skill in the art will readily recognizethat many variations are possible and are within the ambit of thisdisclosure. An initialization state 1202 may be entered upon initialpower up or at other periodic intervals (e.g., once a day) to selfcheck, establish communication, and/or for any other suitable purpose.The OSSD output may remain low (indicating a “do not run” condition tothe associated machinery) while the AUX output may remain high. Thestatus LED may provide a yellow illumination. An OFF state 1204 may beentered if the cable pull switch 200 is not running and has a tensionthat may require adjustment. The status LED may be red as a result andthe OSSD output may remain low. A tensioned off state 1206 may beentered if the cable pull switch 200 is not running but has anacceptable tension on the pull cable 106. The status LED may be red andyellow, while the OSSD output remains low. A user can hit a reset button114 and begin/resume a normal tensioned run state 1208. The normaltensioned run state 1208 is the normal operating state when the tensionis acceptable and the cable pull switch 200 is on. The OSSD output willbe high and the status LED may provide a green light. If the pull cable106 is pulled, the cable pull switch 200 may enter a pulled state 1210wherein the OSSD output will go low and the status LED may beilluminated solid red. Similarly, if the pull cable 106 goes slack, thecable pull switch 200 may enter a slack state 1212 wherein the OSSDoutput will go low and the status LED may be illuminated blinking red.If the tension on the pull cable 106 increases or decreases (e.g., dueto thermal expansion or contraction) outside of an adjustment valuewindow 1002, or outside of a different marginal tension window (forexample, which may be smaller than the non-tripped value window 902 butlarger than the adjustment value window 1002), the cable pull switch 200may enter a marginal tension run state 1214 wherein the OSSD outputswill remain high (allowing the machinery to operate) but the status LEDmay blink green, thereby providing a warning that the tension is closeto an artificial trip point and may require adjustment. Thecommunication module 216 may provide outbound communication of any ofthese states, for example, to a central control computer or system, toprovide feedback to a system manager of a current status and/orrequirement to adjust tension of a particular pull cable 106.

Turning now to FIG. 13, a pull cable excitation module 1300 isillustrated in accordance with various embodiments. The pull cableexcitation module 1300 may, though not necessarily, include many of thesame features and elements as the cable pull switch 200, including ahousing 1302, a tubular body extension 1304, a shaft 1306, a D-ring1308, and a spring 1310. In certain embodiments, the pull cableexcitation module 1300 may even include a polychotomous sensor and/or anoptional processing device 1314 in much the same manner as the cablepull switch 200 to perform the same or similar functionality as thecable pull switch 200 described above in addition to the additionalfeatures described below. Alternatively, the cable excitation module1300 may not perform the same functions as the cable pull switch 200 andmay instead be a separate dedicated functioning element according to thedescription below. A communication module 1316 and communication port1322 may also be included, for example, as described above with respectto communication module 216 and port 222. The communication module 1316may effect communication with a cooperating cable pull switch 200 toinitiate a pull cable excitation state.

In various embodiments, the cable excitation module 1300 also includes acable exciter 1312 mechanically coupled to the shaft 1306. The exciter1312 may be a servo motor, a linear actuator, or another actuatorcapable of manipulating the shaft 1306. The exciter 1312 can, in turn,induce a mechanical tension or vibration onto the pull cable 106.

Turning now to FIG. 14, operation of the cable excitation module 1300 isillustrated in accordance with various embodiments. Coupled to a firstend of the pull cable 106 is a cable pull switch 1400 (which may be thesame as cable pull switch 200 and may include additional features nowdescribed) and attached to the second end of the pull cable 106 is thecable excitation module 1300. In operation, the cable excitation module1300 and the pull cable switch 1400 can enter a cable excitation state.The cable excitation module 1300 can communicate with the cable pullswitch 1400 to initiate the cable excitation state, and either the cableexcitation module 1300 or the cable pull switch 1400 can initiate thecable excitation state. Alternatively or additionally, a separate mastercontroller (not shown) can communicate with one or both of the cableexcitation module 1300 or the cable pull switch 1400 to initiate thecable excitation state. The cable excitation state can be manuallyentered (e.g., by a user), or may periodically scheduled to ensureproper operation of the cable pull system. Once in the cable excitationstate, the cable excitation module 1300 induces a varying tension 1402onto the pull cable 106 by altering the tension exerted on the pullcable 106. This varying tension 1402 can most likely translate to linearmovement of the pull cable 106. The varying tension 1402 may be variedin a slow or quick manner, may be a random pattern or a repeatingpattern, and may be varied by small amounts (e.g., less than wouldnormally be required for a cable pull event) and/or large amounts (e.g.,more than would normally be required for a cable pull event).

The cable pull switch 1400 can detect at the first end of the pull cable106 the varying tension 1402 exerted on the second of the pull cable 106by the pull cable excitation module 1300. The detection may be madethrough one of the various polychotomous sensor techniques discussedabove or via another sensing method. If the pull cable 106 is free ofobstructions or other failures (e.g., is not caught on an eyelet 124),then the cable pull switch 1400 will detect the varying movement 1402 asis shown at 1406. Conversely, if the pull cable 106 is obstructed or isexperiencing a condition that prevents translation of the varyingtension 1402 (e.g., the cable 106 is caught in an eyelet 124 shown at1404), the cable pull switch 1400 may fail to detect the varying tension1402, or fail to detect the varying tension 1402 at an acceptableamplitude as is shown at 1408. In such an instance, the cable pullswitch 1400 may generate an output signal indicative of a pull cablefailure. By this, the cable pull system is tested to avoid a situationwherein the cable pull switch 1400 is inhibited from properly sensing atrue cable pull event through obstruction or other pull cable failure.This also prevents a need for maintenance personnel to manually checkthe pull cables on a regular basis.

In other embodiments, the cable excitation module 1300 may attempt toclear or remove an obstruction or remedy a cable failure by exertinglarger and/or quick tension bursts onto the pull cable 106. The pullcable 106 can be retested thereafter. The module 1300 may also log thecable failure event so that it can be remedied and/or addressed later.

Although the invention or inventions are described throughout thisdisclosure in terms of various apparatuses and devices, one of skill inthe art will readily understand that the operational aspects and/orconfigurations disclosed herein may also be suitably described as one ormore methods.

Various embodiments of the present invention may be embodied in manydifferent forms, including, but in no way limited to, computer programlogic for use with a processor (e.g., a microprocessor, microcontroller, digital signal processor, server computer, or generalpurpose computer), programmable logic for use with a programmable logicdevice (e.g., a Field Programmable Gate Array (FPGA) or other PLD),discrete components, integrated circuitry (e.g., an Application SpecificIntegrated Circuit (ASIC)), or any other means including any combinationthereof.

Computer program logic implementing all or part of the functionalitypreviously described herein may be embodied in various forms, including,but in no way limited to, a source code form, a computer executableform, and various intermediate forms (e.g., forms generated by anassembler, compiler, linker, or locator). Source code may include aseries of computer program instructions implemented in any of variousprogramming languages (e.g., an object code, an assembly language, or ahigh-level language such as C, C++, or JAVA) for use with variousoperating systems or operating environments. The source code may defineand use various data structures and communication messages. The sourcecode may be in a computer executable form (e.g., via an interpreter), orthe source code may be converted (e.g., via a translator, assembler, orcompiler) into a computer executable form.

The computer program may be fixed in any form (e.g., source code form,computer executable form, or an intermediate form) in a tangible storagemedium, such as a semiconductor memory device (e.g., a RAM, ROM, PROM,EEPROM, or Flash-Programmable memory), a magnetic memory device (e.g., adiskette or fixed disk), an optical memory device (e.g., a CD-ROM), a PCcard (e.g., PCMCIA card), or other memory device. The computer programmay be distributed in any form as a removable storage medium withaccompanying printed or electronic documentation (e.g., shrink wrappedsoftware), preloaded with a computer system (e.g., on system ROM orfixed disk), or distributed from a server or electronic bulletin boardover the communication system (e.g., the Internet or World Wide Web).

Hardware logic (including programmable logic for use with a programmablelogic device) implementing all or part of the functionality previouslydescribed herein may be designed using traditional manual methods, ormay be designed, captured, simulated, or documented electronically usingvarious tools, such as Computer Aided Design (CAD), a hardwaredescription language (e.g., VHDL or AHDL), or a PLD programming language(e.g., PALASM, ABEL, or CUPL).

Programmable logic may be fixed either permanently or temporarily in atangible storage medium, such as a semiconductor memory device (e.g., aRAM, ROM, PROM, EEPROM, or Flash-Programmable memory), a magnetic memorydevice (e.g., a diskette or fixed disk), an optical memory device (e.g.,a CD-ROM), or other memory device. The programmable logic may bedistributed as a removable storage medium with accompanying printed orelectronic documentation (e.g., shrink wrapped software), preloaded witha computer system (e.g., on system ROM or fixed disk), or distributedfrom a server or electronic bulletin board over the communication system(e.g., the Internet or World Wide Web).

The present disclosure describes preferred embodiments with reference tothe Figures, in which like numbers represent the same or similarelements. Reference throughout this specification to “one embodiment,”“an embodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

The described features, structures, or characteristics of the inventionmay be combined in any suitable manner in one or more embodiments. Inthe description, numerous specific details are recited to provide athorough understanding of embodiments of the invention. One skilled inthe relevant art will recognize, however, that the invention may bepracticed without one or more of the specific details, or with othermethods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

Although the above discussion discloses various exemplary embodiments ofthe invention, it should be apparent that those skilled in the art canmake various modifications that will achieve some of the advantages ofthe invention without departing from the true scope of the invention.

What is claimed is:
 1. A cable pull switch comprising: a linear opticalsensor array configured to measure a linear displacement of a first endof a pull cable, the linear optical sensor array comprising: at leastone illuminator configured to illuminate a sensor surface of the linearoptical sensor array; and a linearly slidable target including at leastone aperture through which light from the at least one illuminator canilluminate the sensor surface in a pattern to provide a value of lineardisplacement of the linearly slidable target, the linearly slidabletarget configured to be coupled to the first end of the pull cable andto be linearly displaced in relation to the linear displacement of thefirst end of the pull cable; and at least one processing device coupledto the linear optical sensor array, the processing device configured to:receive, from the linear optical sensor array, a value corresponding tothe linear displacement of the first end of the pull cable; determinewhether the value is outside of a non-tripped value window, a firstlimit edge of the non-tripped value window comprising a pull thresholdvalue, the pull threshold value being indicative of a cable pull event;and generate an output signal indicative of the cable pull event inresponse to determining that the value is outside of the non-trippedvalue window on the first end.
 2. The cable pull switch of claim 1,wherein the at least one processing device is further configured to:determine whether the value is outside of the non-tripped value windowon a second side of the non-tripped value window defined by a slackthreshold, the slack threshold indicative of a cable slack event; andgenerate an output signal indicative of the cable slack event inresponse to determining that the value is outside of the non-trippedvalue window on the second side.
 3. The cable pull switch of claim 1,wherein the at least one processing device is further configured to:determine whether the value is outside of the non-tripped value windowon the first end by determining whether the value exceeds the pullthreshold value.
 4. The cable pull switch of claim 1, wherein no outputis generated in response to determining that the value is within thenon-tripped value window on the first end.
 5. The cable pull switch ofclaim 1, wherein the processing device is further configured to: receivean indication of a tension adjustment of the pull cable; and determinewhether the value is outside of an adjustment value window, a firstlimit edge of the adjustment value window comprising a pull adjustmentmargin threshold value, wherein the adjustment value window is a subsetof the non-tripped value window.
 6. The cable pull switch of claim 5,wherein the adjustment value window includes a second limit edgecomprising a slack adjustment margin threshold value.
 7. The cable pullswitch of claim 6, wherein the processing device is further configuredto: generate an output signal when the value approaches one of the pulladjustment margin threshold value and the slack adjustment marginthreshold value.
 8. A cable pull switch comprising: a spring configuredto couple to a first end of a pull cable and configured to at least oneof linearly compress and linearly expand in relation to a lineardisplacement of the first end of the pull cable; an electricalinductance sensor electrically coupled to the spring and configured tosense an electrical inductance value of the spring and a change in theelectrical inductance value of the spring in relationship to the atleast one of the linear compression and the linear expansion of thespring, and configured to measure a linear displacement of a first endof a pull cable; and at least one processing device coupled to theelectrical inductance sensor, the processing device configured to:receive, from the electrical inductance sensor, a value indicative ofthe electrical inductance value of the spring and corresponding to thelinear displacement of the first end of the pull cable; determinewhether the value is outside of a non-tripped value window, a firstlimit edge of the non-tripped value window comprising a pull thresholdvalue, the pull threshold value being indicative of a cable pull event;and generate an output signal indicative of the cable pull event inresponse to determining that the value is outside of the non-trippedvalue window on the first end.
 9. The cable pull switch of claim 8,wherein the at least one processing device is further configured to:determine whether the value is outside of the non-tripped value windowon a second side of the non-tripped value window defined by a slackthreshold, the slack threshold indicative of a cable slack event; andgenerate an output signal indicative of the cable slack event inresponse to determining that the value is outside of the non-trippedvalue window on the second side.
 10. The cable pull switch of claim 8,wherein the at least one processing device is further configured to:determine whether the value is outside of the non-tripped value windowon the first end by determining whether the value exceeds the pullthreshold value.
 11. The cable pull switch of claim 8, wherein no outputis generated in response to determining that the value is within thenon-tripped value window on the first end.
 12. The cable pull switch ofclaim 8, wherein the processing device is further configured to: receivean indication of a tension adjustment of the pull cable; and determinewhether the value is outside of an adjustment value window, a firstlimit edge of the adjustment value window comprising a pull adjustmentmargin threshold value, wherein the adjustment value window is a subsetof the non-tripped value window.
 13. The cable pull switch of claim 12,wherein the adjustment value window includes a second limit edgecomprising a slack adjustment margin threshold value.
 14. The cable pullswitch of claim 13, wherein the processing device is further configuredto: generate an output signal when the value approaches one of the pulladjustment margin threshold value and the slack adjustment marginthreshold value.
 15. A cable pull switch comprising: a sensor configuredto measure a linear displacement of a first end of a pull cable; and atleast one processing device coupled to the sensor, the processing deviceconfigured to: receive, from the sensor, a value corresponding to thelinear displacement of the first end of the pull cable; determinewhether the value is outside of a non-tripped value window, a firstlimit edge of the non-tripped value window comprising a pull thresholdvalue, the pull threshold value being indicative of a cable pull event;generate an output signal indicative of the cable pull event in responseto determining that the value is outside of the non-tripped value windowon the first end; receive an indication of a tension adjustment of thepull cable; and determine whether the value is outside of an adjustmentvalue window, a first limit edge of the adjustment value windowcomprising a pull adjustment margin threshold value, wherein theadjustment value window is a subset of the non-tripped value window. 16.The cable pull switch of claim 15, wherein the at least one processingdevice is further configured to: determine whether the value is outsideof the non-tripped value window on a second side of the non-trippedvalue window defined by a slack threshold, the slack thresholdindicative of a cable slack event; and generate an output signalindicative of the cable slack event in response to determining that thevalue is outside of the non-tripped value window on the second side. 17.The cable pull switch of claim 15, wherein the at least one processingdevice is further configured to: determine whether the value is outsideof the non-tripped value window on the first end by determining whetherthe value exceeds the pull threshold value.
 18. The cable pull switch ofclaim 15, wherein no output is generated in response to determining thatthe value is within the non-tripped value window on the first end. 19.The cable pull switch of claim 15, wherein the adjustment value windowincludes a second limit edge comprising a slack adjustment marginthreshold value.
 20. The cable pull switch of claim 19, wherein theprocessing device is further configured to: generate an output signalwhen the value approaches one of the pull adjustment margin thresholdvalue and the slack adjustment margin threshold value.
 21. A method ofoperating a cable pull switch including a sensor, the method comprising:measuring, via the sensor, a value corresponding to a lineardisplacement of a first end of a pull cable; determining whether thevalue is outside of a non-tripped value window, a first limit edge ofthe non-tripped value window comprising a pull threshold value, the pullthreshold value being indicative of a cable pull event; generating anoutput signal indicative of the cable pull event in response todetermining that the value is outside of the non-tripped value window onthe first end; receiving an indication of a tension adjustment of thepull cable; and determining whether the value is outside of anadjustment value window, a first limit edge of the adjustment valuewindow comprising a pull adjustment margin threshold value, wherein theadjustment value window is a subset of the non-tripped value window. 22.The method of claim 21, further comprising: determining whether thevalue is outside of the non-tripped value window on a second side of thenon-tripped value window defined by a slack threshold, the slackthreshold indicative of a cable slack event; and generating an outputsignal indicative of the cable slack event in response to determiningthat the value is outside of the non-tripped value window on the secondside.
 23. The method of claim 21, further comprising: determiningwhether the value is outside of the non-tripped value window on thefirst end by determining whether the value exceeds the pull thresholdvalue.
 24. The method of claim 21, further comprising: illuminating, viaat least one sensor aperture, a sensor surface with a pattern, thesensor comprising a linear optical sensor array; and determining thevalue corresponding to the linear displacement, based on a lineardisplacement of a linearly slidable target, wherein the linearlyslidable target is configured to be coupled to the first end of the pullcable and to be linearly displaced in relation to the lineardisplacement of the first end of the pull cable.
 25. The method of claim21, further comprising: sensing, via the sensor, an electricalinductance value of a spring, the spring configured to couple to thefirst end of the pull cable and to linearly compress and expand inrelation to the linear displacement of the first end of the pull cable,wherein the value is indicative of the electrical inductance value ofthe spring.